Compilare: user.cpp: In function ‘int main()’: user.cpp:33:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ^ user.cpp:41:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) ^ user.cpp:54:82: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]!='='&&s[j]!='+'&&s[j]!='-'&&s[j]!='x'&&j < s.size()) ^ user.cpp:144:71: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[j]!='+'&&s[j]!='-'&&s[j]!='x'&&j < s.size()) ^ user.cpp:208:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(j == s.size()) ^